Optical record medium judging method and apparatus and focus servo controlling method and apparatus

ABSTRACT

The distances from external surfaces to information record surfaces of the optical record mediums of various types are different from each other. An optical record medium judging method of judging the types of the optical record mediums is provided with the steps of: irradiating an information record surface of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis; moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of the plurality of light beams respectively and the information record surface, the objective lens; receiving a plurality of reflection lights of the plurality of light beams reflected from the information record surface respectively, associated with a change of the relative distance; generating a plurality of focus error signals on the basis of the plurality of received reflection lights respectively; and judging a type of the optical record medium by comparing levels of the generated focus error signals respectively with a predetermined standard level.

This is a divisional of application Ser. No. 08/725,731 filed Oct. 4,1996, now U.S. Pat. No. 5,790,493.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related with a reproducing apparatus in a caseof reproducing, by using one reproducing apparatus, information from aplurality of types of optical record mediums, such as optical disks ofvarious types and the like, to which the information is recorded by aphase pit and the like or a magnetic way, and more particularly, it isrelated with a judging method and apparatus for judging the type of theoptical record medium to be reproduced. It is further related with, inan optical pickup for irradiating a light beam as an informationreproducing light to the plurality of types of optical record mediumsand reproducing the above mentioned information by use of the reflectionlight, a focus servo controlling method and apparatus for carrying out afocus servo control in order to beam-condense (focus) the light beamwhich has an optimal size at a reproducing position of the opticalrecord medium.

2. Description of the Related Art

There is a so-called CD/LD compatible reproducing apparatus which canreproduce a CD (Compact Disk) and a LD (Laser Disk) with one reproducingunit. In this CD/LD compatible reproducing apparatus, a distance from arecord medium surface to an information record surface (namely, athickness of a protecting layer) is common in the CD and the LD (e.g.1.2 mm in common). Thus, it is possible to reproduce both of theseoptical disks by using an optical pickup in which a light beam iscondensed to one focal point.

In this CD/LD compatible reproducing apparatus, as a rising operationprior to reproducing the record information, a focus servo control isneeded for carrying out an optimal focus servo control corresponding tothe type of the optical disk to be reproduced. However, in this case,for example, in order to use a conventionally general astigmatism methodto thereby carry out the focus servo control, prior to carrying out thefocus servo control, it is necessary to do a so-called "focus searchaction" for setting a standard position when carrying out theappropriate focus servo control. This focus search action moves anoptical pickup in a direction perpendicular to the optical disk by apredetermined length to thereby detect an optimal focus position on thebasis of a focus error signal (S-shaped signal) outputted at that time.In the above mentioned CD/LD compatible reproducing apparatus, sincedistances from surfaces of the optical disks to information recordsurfaces are equal to each other in the CD and the LD, a common actionis carried out in both cases in doing the focus search action. Further,in this focus search action, in order to compensate an output powerchange due to the variation of a reflectivity of the optical disk, thecontamination associated with aging of the optical pickup and the like,or a change in a focus servo gain due to the variation of a sensitivityof an optical detector during an optical pickup action and the like, aprocess is carried out which detects a peak value of the above mentionedfocus error signal and re-sets the servo gain corresponding to the peakvalue.

In the above mentioned CD/LD compatible reproducing apparatus, in a caseof judging whether the optical disk mounted in the reproducing apparatusis the CD or the LD, it is judged whether or not the focus servo islocked by moving the optical disk into an area located outside the CDand inside the LD and rotating the optical disk by utilizing a diameterdifference between the CD and the LD. Namely, if it is locked, theoptical disk is judged as the LD. If it is not locked, the optical diskis judged as the CD.

On the other hand, a DVD (Digital Video Disk) is being developed whichgreatly improves a memory capacity as compared with a conventional CDand is a high density record medium to which one movie or the like canbe recorded. Especially, a CD/DVD compatible reproducing apparatus isbeing developed which can reproduce both the DVD and the CD.

When comparing a configuration of the CD with that of the DVD, from theviewpoint of a high density request, the thickness of the protectinglayer of the DVD is set to a thickness (0.6 mm) approximately half ofthat of the protecting layer of the CD. Thus, if trying to reproduceboth of these optical disks by using the optical pickup having one focalpoint, for example, if trying to condense a light beam so as to beoptimal for the DVD, since the protecting layer of the CD through whichthe light beam is passed is thicker than that of the DVD, aberrationsuch as spherical aberration and the like is generated in the lightbeam. This results in a problem that the light beam can not be optimallycondensed with respect to the CD.

In order to solve this problem, one method may be considered in which anaberration correcting element is inserted into an optical path of thelight beam, depending on the type of the optical disk to be reproduced.However, this method will require a mechanical device which puts andretracts the aberration correcting element into and from the opticalpath on the basis of the type of the optical disk to be reproduced.Thus, this method is not suited for miniaturization of the opticalpickup.

A bifocal lens is developed through which it is possible to irradiatetwo light beams focused on different positions on one straight line.This bifocal lens is explained with reference to FIGS.6A and 6B.

As shown in FIG. 6A, the bifocal lens comprises a diffraction grating Hand an objective lens R arranged on one optical path. A light beam Lmade into a parallel light by a collimator lens C is divided into threebeams of a 0 order light, a +1 order light and a-1 order light by thediffraction grating H. By using a difference between optical pathlengths of the 0 order light and the +1 order light among them, the 0order light and the +1 order light are made focused on differentpositions on one straight line. More actually, this bifocal lens isadapted such that the +1 order light is focused on a position furtherfrom the objective lens R than the 0 order light, and that the 0 orderlight is optimally beam-condensed on the information record surface ofthe DVD (e.g. 0.6 mm from the disk surface), and also as shown in FIG.6B, the +1 order light is optimally beam-condensed on the informationrecord surface of the CD (e.g. 1.2 mm from the disk surface).

If using this bifocal lens, it is possible to use one optical pickup tothereby reproduce both of the CD and the DVD.

Even in a case of using the above mentioned bifocal lens to therebyreproduce information, similarly to the conventional CD/LD compatiblereproducing apparatus, the focus search action is required.

From the viewpoint of a high density request, the DVD is superior inlinear velocity of record information to the CD. Thus, the focus servogain and a focus servo frequency band in the focus search action aredifferent between the CD and the DVD. For the focus servo frequencyband, more actually, it is necessary that the DVD is widely set on ahigher frequency side than the CD.

If trying to apply the conventional focus search action to such a CD/DVDcompatible reproducing apparatus, it is necessary to verify twodifferent focus servo gains and focus servo frequency bands and set thefocus servo gain and the focus servo frequency band which are adapted tothe mounted optical disk. This results in a problem of requiring anunnecessary time for the focus servo action.

Even when judging the optical disk mounted in the CD/DVD compatiblereproducing apparatus, since a radius of the CD is equal to that of theDVD, there is a problem that a conventional disk judging method can notbe used. In combination with this problem and the above mentionedproblem in setting the focus servo gain and the focus servo frequencyband, judging of the optical disk and setting of the focus servo gainand the focus servo frequency band are separately carried out, so thatit is impossible to carry out a rapid rising operation at the beginningof reproducing the record information, which is another problem.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an opticalrecord medium judging method and apparatus, and a focus servocontrolling method and apparatus, which can carry out a rapid risingoperation in a compatible reproducing apparatus for reproducing opticalrecord mediums of various types e.g. a CD/DVD compatible reproducingapparatus.

The above object of the present invention can be achieved by an opticalrecord medium judging method of judging types of optical record mediums,which distances from external surfaces thereof to information recordsurfaces thereof recorded with record information are different fromeach other. The optical record medium judging method is provided withthe steps of: irradiating an information record surface of an opticalrecord medium to be reproduced with a plurality of light beams to befocused on different positions on one optical axis; moving, so as tochange a relative distance parallel to said one optical axis between anobjective lens for prescribing focal points of the plurality of lightbeams respectively and the information record surface, the objectivelens; receiving a plurality of reflection lights of the plurality oflight beams reflected from the information record surface respectively,associated with a change of the relative distance; generating aplurality of focus error signals on the basis of the plurality ofreceived reflection lights respectively; and judging a type of theoptical record medium by comparing levels of the generated focus errorsignals respectively with a predetermined standard level.

According to the optical record medium judging method of the presentinvention, the information record surface of the optical record mediumis irradiated with a plurality of light beams to be focused on differentpositions on one optical axis. Then, the objective lens is moved, sothat the relative distance parallel to the optical axis between theobjective lens and the information record surface is changed. Then, aplurality of reflection lights of the plurality of light beams reflectedfrom the information record surface respectively are received inassociation with the change of the relative distance. Then, a pluralityof focus error signals are generated on the basis of the plurality ofreceived reflection lights respectively. Finally, the type of theoptical record medium is judged by comparing levels of the generatedfocus error signals respectively with a predetermined standard level.

Accordingly, it is possible to judge the types of the optical recordmediums even if the diameters thereof are same to each other as in thecase of the CD and the DVD. Namely, as long as the distances between theexternal surfaces to the information record surfaces are different fromeach other, the types of the optical record mediums can be judgedaccording to the optical record medium judging method of the presentinvention.

As one aspect of the optical record medium judging method of the presentinvention, the optical record mediums include first and second opticalrecord mediums which distances from the external surfaces thereof to theinformation record surfaces thereof are different from each other. Theirradiating step is provided with the steps of irradiating theinformation record surface with a first light beam to reproduce therecord information from the first optical record medium, and irradiatingthe information record surface with a second light beam to reproduce therecord information from the second optical record medium, the secondlight beam having a focal point farther from the objective lens than thefirst light beam. The receiving step is provided with the steps ofreceiving a first reflection light of the first light beam reflectedfrom the information record surface, and receiving a second reflectionlight of the second light beam reflected from the information recordsurface. The focus error signal generating step is provided with thesteps of generating a first focus error signal on the basis of thereceived first reflection light, and generating a second focus errorsignal on the basis of the received second reflection light. The judgingstep is provided with the steps of judging the type of the opticalrecord medium as the first optical record medium if at least one of thelevels of the first and second focus error signals is equal to or higherthan the predetermined standard level, and judging the type as thesecond optical record medium if both of the levels are lower than thepredetermined standard level.

According to this aspect of the present invention, the informationrecord surface is irradiated with the first light beam to reproduce therecord information from the first optical record medium, and theinformation record surface is irradiated with the second light beam toreproduce the record information from the second optical record medium.Here, the second light beam has a focal point farther from the objectivelens than the first light beam. Then, the first reflection light of thefirst light beam reflected from the information record surface isreceived, and the second reflection light of the second light beamreflected from the information record surface is received. Then, thefirst focus error signal is generated on the basis of the received firstreflection light, and the second focus error signal is generated on thebasis of the received second reflection light. Finally, the type of theoptical record medium is judged as the first optical record medium if atleast one of the levels of the first and second focus error signals isequal to or higher than the predetermined standard level, and the typeis judged as the second optical record medium if both of the levels arelower than the predetermined standard level.

Accordingly, it is possible to judge the first and second optical recordmediums even if the diameters of the first and second optical recordmediums are same to each other as in the case of the CD and the DVD.Namely, as long as the distances between the external surfaces to theinformation record surfaces are different between the first and secondoptical record mediums, the types of the optical record mediums can bejudged according to this aspect of the present invention.

In this aspect of the present invention, in the irradiating step, thefirst light beam may be a 0 order light generated by a bifocal lens, andthe second light beam may be a +1 order light generated by the bifocallens. Thus, it is possible to irradiate the information record surfacewith a plurality of light beams by employing a relatively simpleconstruction i.e., the bifocal lens, to the optical system while theoptical record medium judging operation including the focus searchaction can be efficiently and reliably performed.

The above object of the present invention can be also achieved by afocus servo controlling method of judging types of optical recordmediums, on which record informations are recorded at linear velocitiesdifferent from each other, and setting a focus servo gain and a focusservo frequency band corresponding to each of the types of the opticalrecord mediums. The focus servo controlling method is provided the stepsof: irradiating an information record surface recorded with recordinformation of an optical record medium to be reproduced with aplurality of light beams to be focused on different positions on oneoptical axis; moving, so as to change a relative distance parallel tosaid one optical axis between an objective lens for prescribing focalpoints of the plurality of light beams respectively and the informationrecord surface, the objective lens on the basis of a control signal;receiving a plurality of reflection lights of the plurality of lightbeams reflected from the information record surface respectively,associated with a change of the relative distance; generating aplurality of focus error signals on the basis of the plurality ofreceived reflection lights respectively; judging a type of the opticalrecord medium by comparing peak values of the generated focus errorsignals respectively with a predetermined standard level; setting thefocus servo gain and the focus servo frequency band on the basis of thepeak values; and generating the control signal, wherein the focus servogain and the focus servo frequency band are set in the setting step byrepeating following operations with respect to the linear velocities ofthe optical record mediums one after another: firstly, the controlsignal to move the objective lens at a moving speed corresponding to afastest linear velocity among the linear velocities is generated by thecontrol signal generating step; the focus servo gain and the focus servofrequency band are set on the basis of a peak value of a focus errorsignal generated by moving the objective lens at the moving speedcorresponding to the fastest linear velocity by the setting step, if thejudged type of the optical record medium is one recorded with the recordinformation at the fastest linear velocity; secondly, if the judged typeof the optical record medium is not one recorded with the recordinformation at the fastest linear velocity, the control signal to movethe objective lens at a moving speed corresponding to a second fastestlinear velocity among the linear velocities is generated by the controlsignal generating step; and the focus servo gain and the focus servofrequency band are set on the basis of a peak value of a focus errorsignal generated by moving the objective lens at the moving speedcorresponding to the second fastest linear velocity by the setting step,if the judged type of the optical record medium is one recorded with therecord information at the second fastest linear velocity.

According to the focus servo controlling method of the presentinvention, the information record surface is irradiated with a pluralityof light beams to be focused on different positions on one optical axis.Then, the objective lens is moved on the basis of the control signalgenerated by the control signal generating step, so that the relativedistance parallel to the optical axis between the objective lens and theinformation record surface is changed. Then, a plurality of reflectionlights of the plurality of light beams reflected from the informationrecord surface respectively are received in association with the changeof the relative distance. Then, a plurality of focus error signals aregenerated on the basis of the plurality of received reflection lightsrespectively. Then, the type of the optical record medium is judged bycomparing peak values of the generated focus error signals respectivelywith a predetermined standard level. Then, the focus servo gain and thefocus servo frequency band are set on the basis of the peak values. Atthis time, the focus servo gain and the focus servo frequency band areset in the setting step by repeating following operations with respectto the linear velocities of the optical record mediums one afteranother. That is to say, firstly, the control signal to move theobjective lens at the moving speed corresponding to the fastest linearvelocity is generated. Then, if the judged type of the optical recordmedium is one recorded with the record information at the fastest linearvelocity, the focus servo gain and the focus servo frequency band areset on the basis of the peak value of the focus error signal generatedwhile the objective lens is moved at the moving speed corresponding tothe fastest linear velocity. Secondly, if the judged type of the opticalrecord medium is not one recorded with the record information at thefastest linear velocity, the control signal to move the objective lensat the moving speed corresponding to the second fastest linear velocityis generated. Then, if the judged type of the optical record medium isone recorded with the record information at the second fastest linearvelocity, the focus servo gain and the focus servo frequency band areset on the basis of the peak value of the focus error signal generatedwhile the objective lens is moved at the moving speed corresponding tothe second fastest linear velocity. Then, until the optical recordmedium is appropriately judged and the focus servo gain and the focusservo frequency band are appropriately set, these operations arerepeated.

Accordingly, the setting operations of the focus servo gain and thefocus servo frequency band can be performed efficiently within arelatively short time period. Further, the judging operation of theoptical record medium and the setting operations of the focus servo gainand the focus servo frequency band can be performed in one consecutiveprocedure. Therefore, it is possible to speedily perform the risingoperation of the compatible reproducing apparatus, which can reproducethe optical record mediums of different types even if the diametersthereof are same to each other as in the case of the CD and the DVD.Namely, as long as the linear velocities of recording the informationare different from each other, the rising operation can be speedilyperformed according to the focus servo controlling method of the presentinvention.

As one aspect of the focus servo controlling method of the presentinvention, the optical record mediums include a first optical recordmedium, on which the record information is recorded at a first linearvelocity, and a second optical record medium, on which the recordinformation is recorded at a second linear velocity lower than the firstlinear velocity and which distance from the external surface thereof tothe information record surface thereof is different from that of thefirst optical record medium. The moving step is provided with the stepof firstly moving the objective lens at a first moving speedcorresponding to the first linear velocity. The receiving step isprovided with the step of firstly receiving the plurality of reflectionlights associated with the change of the relative distance in thefirstly moving step. The focus error generating step is provided withthe step of firstly generating the plurality of focus error signals onthe basis of the reflection lights received by the firstly receivingstep. The method is further provided with the step of firstlycalculating the peak values of the focus error signals respectivelygenerated by the firstly generating step. The judging step is providedwith the steps of judging the optical record medium as the first opticalrecord medium if at least one of the peak values calculated by thefirstly calculating step is equal to or higher than the predeterminedstandard level, and judging the optical record medium as the secondoptical record medium if all of the peak values calculated by thefirstly calculating step are lower than the predetermined standardlevel. The setting step is provided with the step of firstly setting thefocus servo gain and the focus servo frequency band on the basis of ahighest peak value of the peak values calculated by the firstlycalculating step, if the optical record medium is judged as the firstoptical record medium. The moving step is further provided with the stepof secondly moving the objective lens at a second moving speed, whichcorresponds to the second linear velocity and which is lower than thefirst moving speed, if the optical record medium is judged as the secondoptical record medium. The receiving step is further provided with thestep of secondly receiving the plurality of reflection lights associatedwith the change of the relative distance in the secondly moving step.The focus error generating step is further provided with the step ofsecondly generating the plurality of focus error signals on the basis ofthe reflection lights received by the secondly receiving step. The focuserror controlling method is further provided with the step of secondlycalculating the peak values of the focus error signals respectivelygenerated by the secondly generating step. The setting step is providedwith the step of secondly setting the focus servo gain and the focusservo frequency band on the basis of a highest peak value of the peakvalues calculated by the secondly calculating step.

According to this aspect of the present invention, the objective lens isfirstly moved at the first moving speed corresponding to the firstlinear velocity. Then, the plurality of reflection lights associatedwith the change of the relative distance in the firstly moving step arefirstly received. Then, the plurality of focus error signals are firstlygenerated on the basis of the reflection lights received by the firstlyreceiving step. Then, the peak values of the focus error signalsrespectively generated by the firstly generating step are firstlycalculated. Then, the optical record medium is judged as the firstoptical record medium if at least one of the peak values calculated bythe firstly calculating step is equal to or higher than thepredetermined standard level. On the other hand, the optical recordmedium is judged as the second optical record medium if all of the peakvalues calculated by the firstly calculating step are lower than thepredetermined standard level. Then, the focus servo gain and the focusservo frequency band are firstly set on the basis of the highest peakvalue of the peak values calculated by the firstly calculating step, ifthe optical record medium is judged as the first optical record medium.After that, if the optical record medium is judged as the second opticalrecord medium, the objective lens is secondly moved at the second movingspeed. Here, the second moving speed corresponds to the second linearvelocity and is lower than the first moving speed. Then, the pluralityof reflection lights associated with the change of the relative distancein the secondly moving step are secondly received. Then, the pluralityof focus error signals are secondly generated on the basis of thereflection lights received by the secondly receiving step. Then, thepeak values of the focus error signals respectively generated by thesecondly generating step are secondly calculated. Finally, the focusservo gain and the focus servo frequency band are secondly set on thebasis of the highest peak value of the peak values calculated by thesecondly calculating step.

Accordingly, the setting operations of the focus servo gain and thefocus servo frequency band can be performed efficiently within arelatively short time period. Further, the judging operation of theoptical record medium and the setting operations of the focus servo gainand the focus servo frequency band can be performed in one consecutiveprocedure. Therefore, it is possible to speedily perform the risingoperation of the compatible reproducing apparatus, which can reproducethe first and second optical record mediums even if the diameters of thefirst and second optical record medium are same to each other as in thecase of the CD and the DVD. Namely, as long as the distances between theexternal surfaces to the information record surfaces are differentbetween the first and second optical record medium, the rising operationcan be speedily performed according to this aspect of the presentinvention.

In this aspect of the present invention, in the irradiating step, thefirst light beam may be a 0 order light generated by a bifocal lens, andthe second light beam may be a +1 order light generated by the bifocallens. Thus, it is possible to irradiate the information record surfacewith a plurality of light beams by employing a relatively simpleconstruction i.e., the bifocal lens, to the optical system while thefocus servo control operation including the focus search action can beefficiently and reliably performed.

The above object of the present invention can be also achieved by anoptical record medium judging apparatus for judging types of opticalrecord mediums, which distances from external surfaces thereof toinformation record surfaces thereof recorded with record information aredifferent from each other. The optical record medium judging apparatusis provided with: a light irradiating device for irradiating aninformation record surface of an optical record medium to be reproducedwith a plurality of light beams to be focused on different positions onone optical axis; a lens moving device for moving, so as to change arelative distance parallel to said one optical axis between an objectivelens for prescribing focal points of the plurality of light beamsrespectively and the information record surface, the objective lens; alight receiving device for receiving a plurality of reflection lights ofthe plurality of light beams reflected from the information recordsurface respectively, associated with a change of the relative distance;a focus error generating device for generating a plurality of focuserror signals on the basis of the plurality of received reflectionlights respectively; and a judging device for judging a type of theoptical record medium by comparing levels of the generated focus errorsignals respectively with a predetermined standard level.

As one aspect of the optical record medium judging apparatus of thepresent invention, the optical record mediums include first and secondoptical record mediums which distances from the external surfacesthereof to the information record surfaces thereof are different fromeach other. The light irradiating device is provided with a device forirradiating the information record surface with a first light beam toreproduce the record information from the first optical record medium,and irradiating the information record surface with a second light beamto reproduce the record information from the second optical recordmedium, the second light beam having a focal point farther from theobjective lens than the first light beam. The light receiving device isprovided with a first receiving device for receiving a first reflectionlight of the first light beam reflected from the information recordsurface, and a second receiving device for receiving a second reflectionlight of the second light beam reflected from the information recordsurface. The focus error signal generating device is provided with afirst generating device for generating a first focus error signal on thebasis of the received first reflection light, and a second generatingdevice for generating a second focus error signal on the basis of thereceived second reflection light. The type judging device is providedwith a first judging device for judging the type of the optical recordmedium as the first optical record medium if at least one of the levelsof the first and second focus error signals is equal to or higher thanthe predetermined standard level, and a second judging device forjudging the type as the second optical record medium if both of thelevels are lower than the predetermined standard level.

In this aspect of the present invention, in the light irradiatingdevice, the first light beam may be a 0 order light generated by abifocal lens, and the second light beam may be a +1 order lightgenerated by the bifocal lens.

According to the optical record medium judging apparatus of the presentinvention, the aforementioned optical record medium judging method ofthe present invention can be certainly performed, and the sameadvantageous effects as those of the optical record medium judgingmethod can be achieved by the optical record medium judging apparatusaccording to the present invention.

The above object of the present invention can be also achieved by afocus servo controlling apparatus for judging types of optical recordmediums, on which record informations are recorded at linear velocitiesdifferent from each other, and setting a focus servo gain and a focusservo frequency band corresponding to each of the types of the opticalrecord mediums. The focus servo controlling apparatus is provided with:a light irradiating device for irradiating an information record surfacerecorded with record information of an optical record medium to bereproduced with a plurality of light beams to be focused on differentpositions on one optical axis; a lens moving device for moving, so as tochange a relative distance parallel to said one optical axis between anobjective lens for prescribing focal points of the plurality of lightbeams respectively and the information record surface, the objectivelens on the basis of a control signal; a light receiving device forreceiving a plurality of reflection lights of the plurality of lightbeams reflected from the information record surface respectively,associated with a change of the relative distance; a focus errorgenerating device for generating a plurality of focus error signals onthe basis of the plurality of received reflection lights respectively; atype judging device for judging a type of the optical record medium bycomparing peak values of the generated focus error signals respectivelywith a predetermined standard level; a servo setting device for settingthe focus servo gain and the focus servo frequency band on the basis ofthe peak values; and a control signal generating device for generatingthe control signal, wherein the servo setting device sets the focusservo gain and the focus servo frequency band by repeating followingoperations with respect to the linear velocities of the optical recordmediums one after another: firstly, the control signal generating devicegenerates the control signal to move the objective lens at a movingspeed corresponding to a fastest linear velocity among the linearvelocities; the servo setting device sets the focus servo gain and thefocus servo frequency band on the basis of a peak value of a focus errorsignal generated by moving the objective lens at the moving speedcorresponding to the fastest linear velocity, if the judged type of theoptical record medium is one recorded with the record information at thefastest linear velocity; secondly, if the judged type of the opticalrecord medium is not one recorded with the record information at thefastest linear velocity, the control signal generating device generatesthe control signal to move the objective lens at a moving speedcorresponding to a second fastest linear velocity among the linearvelocities; and the servo setting device sets the focus servo gain andthe focus servo frequency band on the basis of a peak value of a focuserror signal generated by moving the objective lens at the moving speedcorresponding to the second fastest linear velocity, if the judged typeof the optical record medium is one recorded with the record informationat the second fastest linear velocity.

As one aspect of the focus servo controlling apparatus of the presentinvention, the optical record mediums include a first optical recordmedium, on which the record information is recorded at a first linearvelocity, and a second optical record medium, on which the recordinformation is recorded at a second linear velocity lower than the firstlinear velocity and which distance from the external surface thereof tothe information record surface thereof is different from that of thefirst optical record medium. The lens moving device is provided with afirst moving device for firstly moving the objective lens at a firstmoving speed corresponding to the first linear velocity. The lightreceiving device is provided with a first receiving device for firstlyreceiving the plurality of reflection lights associated with the changeof the relative distance of the objective lens moved by the first movingdevice. The focus error generating device is provided with a firstgenerating device for firstly generating the plurality of focus errorsignals on the basis of the reflection lights received by the firstreceiving device. The apparatus is further provided with a firstcalculating device for firstly calculating the peak values of the focuserror signals respectively generated by the first generating device. Thetype judging device is provided with a first judging device for judgingthe optical record medium as the first optical record medium if at leastone of the peak values calculated by the first calculating device isequal to or higher than the predetermined standard level, and a secondjudging device for judging the optical record medium as the secondoptical record medium if all of the peak values calculated by the firstcalculating device are lower than the predetermined standard level. Theservo setting device is provided with a first setting device for firstlysetting the focus servo gain and the focus servo frequency band on thebasis of a highest peak value of the peak values calculated by the firstcalculating device, if the optical record medium is judged as the firstoptical record medium. The lens moving device is further provided with asecond moving device for secondly moving the objective lens at a secondmoving speed, which corresponds to the second linear velocity and whichis lower than the first moving speed, if the optical record medium isjudged as the second optical record medium. The light receiving deviceis further provided with a second receiving device for secondlyreceiving the plurality of reflection lights associated with the changeof the relative distance of the objective lens moved by the secondmoving device. The focus error generating device is further providedwith a second generating device for secondly generating the plurality offocus error signals on the basis of the reflection lights received bythe second receiving device. The focus servo controlling apparatus isfurther provided with a second calculating device for secondlycalculating the peak values of the focus error signals respectivelygenerated by the second generating device; and the servo setting deviceis provided with a second setting device for secondly setting the focusservo gain and the focus servo frequency band on the basis of a highestpeak value of the peak values calculated by the second calculatingdevice.

In this aspect of the present invention, in the light irradiatingdevice, the first light beam may be a 0 order light generated by abifocal lens, and the second light beam may be a +1 order lightgenerated by the bifocal lens.

According to the focus servo controlling apparatus of the presentinvention, the aforementioned focus servo controlling method of thepresent invention can be certainly performed, and the same advantageouseffects as those of the focus servo controlling method can be achievedby the focus servo controlling apparatus according to the presentinvention.

In this manner, according to the above described optical record mediumjudging method and apparatus of the present invention, it is possible tojudge the CD and the DVD in the CD/DVD compatible reproducing apparatushaving the bifocal lens. Further, according to the above described focusservo controlling method and apparatus of the present invention, it ispossible to rapidly set the focus servo gain and the focus servofrequency band in parallel to the above mentioned judging action.Consequently, it is possible to carry out the rapid rising operation inthe CD/DVD compatible reproducing apparatus.

The nature, utility, and further features of this invention will be moreclearly apparent from the following detailed description with respect topreferred embodiments of the invention when read in conjunction with theaccompanying drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram showing a principle of an optical disk judgment andshowing a focus error signal generated in conjunction with the moving upaction of a bifocal lens;

FIG. 1B is a diagram showing the focus error signals in cases of the DVDand the CD respectively;

FIG. 2 is a block diagram showing a configuration of a reproducingapparatus of an embodiment;

FIG. 3 is a flow chart showing an operation of the reproducing apparatusof the embodiment;

FIG.4 is a timing chart (in a case of the CD) showing an operation ofthe reproducing apparatus of the embodiment;

FIG.5 is a timing chart (in a case of the DVD) showing an operation ofthe reproducing apparatus of the embodiment;

FIG. 6A is a block diagram showing a configuration of a bifocal lens inone operating status; and

FIG. 6B is a block diagram showing a configuration of a bifocal lens inanother operating status.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Next, a preferred embodiment of the present invention will be explainedwith reference to the drawings.

(I) Principle of Optical Disk Judgment

Before explaining a construction and operation of an embodiment, theprinciple of the optical disk judgment in this embodiment is explainedwith reference to FIGS. 1A and 1B.

As mentioned above, the two light beams L from an optical pickup havinga bifocal lens are set such that the +1 order light is optimallybeam-condensed on the CD and the 0 order light is optimallybeam-condensed on the DVD, and the +1 order light is longer in focallength than the 0 order light. Thus, for example, as shown in FIG. 1A,when the bifocal lens is moved up for the CD, at first the +1 orderlight is beam-condensed on an information record surface of the CD andthen a focus error signal Sfe is detected. Next, a pseudo signal of thefocus error signal Sfe induced by a fact that a reflection light fromthe optical disk of the +1 order light is passed through an optical pathof the 0 order light is detected. Finally, a focus error signal Sfecorresponding to the 0 order light is detected. Here, as mentionedabove, an optical system is set such that the 0 order light is optimallybeam-condensed for the DVD and the +1 order light is optimallybeam-condensed for the CD. Thus, for a converse combination thereof, theoptimal beam-condensing condition is not kept, for example, because ofgeneration of spherical aberration. Therefore, in a case that theoptical disk is the CD, the focus error signal Sfe corresponding to the+1 order light has the highest level, and the focus error signal Sfecorresponding to the 0 order light has the lowest level, In contrastwith this, in a case that the optical disk is the DVD, the focus errorsignal Sfe corresponding to the 0 order light has the highest level, andthe focus error signal Sfe corresponding to the +1 order light has thelowest level.

When comparing a level of the focus error signal Sfe corresponding tothe 0 order light in a case that the optical disk is the DVD with alevel of the focus error signal corresponding to the +1 order light in acase that the optical disk is the CD, since a spectral ratio of adiffraction grating H of the bifocal lens is set such that a lightquantity of the 0 order light is larger than that of the +1 order lightin the light beam L, the level (a symbol FE2 of FIG. 1B) of the focuserror signal Sfe corresponding to the 0 order light in the case that theoptical disk is the DVD is higher than the level (a symbol FE1 of FIG.1B) of the focus error signal Sfe corresponding to the +1 order light inthe case that the optical disk is the CD as shown in FIG. 1B.

Therefore, a predetermined threshold TH1 is defined as a value betweenthe level of the focus error signal Sfe corresponding to the 0 orderlight in the case that the optical disk is the DVD and the level of thefocus error signal Sfe corresponding to the +1 order light in the casethat the optical disk is the CD. Then, if one of the levels of thedetected focus error signals Sfe is higher than the threshold TH1, theoptical disk to which at that time the light beam L is irradiated can bejudged as the DVD. If all the levels are lower than the threshold TH1,the optical disk to which at that time the light beam L is irradiatedcan be judged as the CD.

More actually explaining with reference to FIG. 1B, when the bifocallens is moved up in a short time (refer to a symbol (A) of FIG. 1B) andthen moved down (refer to a symbol (B) of FIG. 1B), at first the 0 orderlight is beam-condensed on the information record surface, and then the+1 order light is beam-condensed. Thus, if the optical disk is the CD, alevel of a third focus error signal Sfe (focus error signal Sfecorresponding to the +1 order light) among three focus error signals Sfedetected in a moving down process is higher than the other two focuserror signals Sfe. However, it is lower than the threshold TH1 even inthis case. And, if the optical disk is the DVD, a level of a first focuserror signal Sfe (focus error signal Sfe corresponding to the 0 orderlight) among the three focus error signals Sfe detected in the movingdown process is higher than the other two focus error signals Sfe. Andthat, it is higher than the threshold TH1 in this case. Therefore, whenthe level of one of the focus error signals Sfe detected in the movingdown process of the bifocal lens exceeds the threshold TH1, the opticaldisk is judged as the DVD. When the levels of all the focus errorsignals Sfe do not exceed the threshold TH1, the optical disk is judgedas the CD.

(II) Construction and Operation

The construction and operation of the embodiment of the presentinvention based on the above mentioned principle of the optical disk isexplained with reference to FIGS. 2 to 5. FIG.2 is a schematic blockdiagram of a DVD/CD compatible reproducing apparatus in accordance withthe present invention. FIG.3 is the flow chart showing the operation ofthe DVD/CD compatible reproducing apparatus shown in FIG. 2. FIGS. 4 and5 are the timing charts showing the operations of the DVD/CD compatiblereproducing apparatus shown in FIG. 2. Incidentally, the timing chart inFIG. 4 shows the operation in a case that the CD is mounted in theDVD/CD compatible reproducing apparatus. The timing chart in FIG. 5shows the operation in a case that the DVD is mounted.

The case in which the CD is reproduced as the optical disk is firstlyexplained in the following embodiment.

At first, the configuration of the DVD/CD compatible reproducingapparatus in accordance with the present invention is explained withreference to FIG.2.

In a DVD/CD compatible reproducing apparatus S₁ shown in FIG. 2, in anoptical disk 1 that is the CD, information is recorded on an informationtrack TR by a phase pit or a magnetic record mark. A light spot Sp isformed by the light beam L from a laser diode (not shown ) included inan optical pickup P. In FIG.2, as an optical system installed within theoptical pickup P, only devices related especially with the presentinvention are described, and general devices, such as a mirror, adeflecting plate and the like, are omitted.

A light-receiving device 2 is included within the optical pickup P, andis a four-divided photo detector. This light-receiving device 2 receivesa reflection light which is reflected from the light spot Sp and towhich astigmatism is given by a cylindrical lens ER, and outputs adetection signal.

A subtracter 3 mutually subtracts signals, in which two detectorsopposite to each other in the light-receiving device 2 are synthesizedrespectively, and outputs the focus error signal Sfe.

A LPF (Low Pass Filter) 4 removes an unnecessary frequency componentequal to or more than a sampling frequency of an A/D converter 6described later from the focus error signal Sfe, and converts into awave form that can be used as the focus error signal Sfe.

A VCA (Voltage Controlled Amplifier) circuit 5 sets a focus servo gainon the basis of a control signal Sc1 described later.

The A/D converter 6 converts the focus error signal Sfe amplified on thebasis of the set focus servo gain into a digital signal.

A digital equalizer circuit 7 is composed of a digital filter and thelike, and sets, on the basis of a control signal Sc2 described later, afocus servo frequency band corresponding to the focus error signal Sfeconverted into the digital signal.

A PWM (Pulse Width Modulation) circuit 8 generates, on the basis of acontrol signal Sc3 described later, generates a focus drive signal Sfdhaving a pulse width corresponding to a level of the inputted focuserror signal Sfe. At this time, on the basis of the control signal Sc3,the focus drive signal Sfd is generated so as to drive a bifocal lens 11as an objective lens as described later at the moving speed for anoperation described later.

A driver circuit 9 amplifies the focus drive signal Sfd and outputs itto an actuator 10 described later.

The actuator 10 is composed of an electromagnet coil and the like, anddrives the bifocal lens 11 into an optical axis direction (focusdirection) of the light beam L, on the basis of the focus drive signalSfd.

An adder 12 adds all the detection signals outputted from thelight-receiving device 2 to thereby generate a read RF (Radio Frequency)signal. This read RF signal is outputted to an demodulator (not shown)and the like as a reproduction signal including record information, andalso outputted to an RF envelope circuit 13.

The RF envelope circuit 13 is composed of a low pass filter and thelike, and outputs an amplitude amount (envelope) of the read RF signal,from which a high frequency signal due to a pit is removed among the RFsignal.

The LPF 14 extracts only a low band frequency component from theenvelope.

An A/D converter 15 converts the envelope into a digital signal andoutputs it to a servo controller 16.

The servo controller 16 calculates, on the basis of the focus errorsignal Sfe, a peak value thereof, and also, on the basis of the maximumpeak value of the peak values, outputs the control signal Sc1 to set thefocus servo gain, the control signal Sc2 to set the focus servofrequency band and the control signal Sc3 to control the moving speed ofthe bifocal lens 11. In addition to these functions, the servocontroller 16 controls the whole focus servo action in the DVD/CDcompatible reproducing apparatus S₁. Information required for theseoperations of the servo controller 16 is transiently stored in a RAM(Random Access Memory) 17.

Next, rising operations including a judging action of the optical disk 1and the focus servo gain and focus servo frequency band setting actionin the DVD/CD compatible reproducing apparatus S₁ are explained withreference to FIGS. 3 to 5.

The rising operations shown in FIGS. 3 to 5 are mainly carried out underthe control of the servo controller 16. At first, under a first movingspeed corresponding to the linear velocity of the record informationrecorded in the DVD, the bifocal lens 11 is, for example, driven toreciprocate twice (respective two times in moving up and moving downactions) in the optical axis direction of the light beam L. The disk isjudged by a method shown in FIGS. 1A and 1B, on the basis of the peakvalue of the focus error signal Sfe detected at that time. If it isjudged as the DVD, the focus servo gain and the focus servo frequencyband are set by using the maximum value of the detected peak value. Onthe other hand, in a case that it is judged as the CD, at a secondmoving speed (slower than the first moving speed) corresponding to thelinear velocity of the record information recorded in the CD, thebifocal lens 11 is, for example, further driven to reciprocate twice(respective two times in the moving up and moving down actions) in theoptical axis direction of the light beam L. The focus servo gain and thefocus servo frequency band are set on the basis of the maximum peakvalue of the focus error signals Sfe detected at that time. In FIGS. 4and 5, a "+" side of the focus drive signal Sfd corresponds to themoving up action (a direction approaching the optical disk 1) of thebifocal lens 11, and a "-" side corresponds to the moving down action (adirection going away from the optical disk 1) of the bifocal lens 11.Further, in FIGS. 3 to 5, "UH" is a focus drive signal Sfd correspondingto an upper limit position of the bifocal lens 11. "UL" is a focus drivesignal Sfd corresponding to a lower limit position of the bifocal lens11.

The followings are explained, assuming that the CD is mounted in theDVD/CD compatible reproducing apparatus S₁.

As shown in FIG. 3, at first a register and the like included in theservo controller 16 are initialized (Step S1), in the rising operationsin the DVD/CD compatible reproducing apparatus S₁ in which the CD ismounted. In the step S1 in FIG. 3, a reference numeral M denotes thenumber of the moving up and moving down movements of the bifocal lens11. Actually, as shown in FIG.4 or 5, a first moving up processcorresponds to M="0", and a next moving down process corresponds toM="1".

When the initialization (Step 1) is ended, whether or not the opticaldisk 1 is mounted in the reproducing apparatus S₁ is detected by adetecting device (not shown in FIG. 2) (Step S2). In a case that it isnot mounted (Step S2; NO), the operation is waited as it is. In a casethat the optical disk 1 is mounted (Step S2 YES), the optical disk 1 isrotated by a spindle motor (not shown in FIG.2) (Step S3).

When the optical disk is started to be rotated (Step S3), the focusdrive signal Sfd is outputted, on the basis of the control signal Sc3,so as to move down the bifocal lens 11 in a short time (Step S4, andrefer to a symbol (A) of FIG. 4). Then, it is judged whether or not thebifocal lens 11 moves down to a lower limit position (Step S5). Namely,it is checked whether or not |Sfd|≧UL. When the bifocal lens 11 is moveddown to a lower limit position (Step S5; YES), the operation is waitedfor a time period T1 corresponding to a preparing period (for example, anecessary period until a movement of the lens becomes stable) to detectthe focus error signal Sfe (Step S6). After that, it is set such thatthe bifocal lens 11 is moved up at the first moving speed correspondingto the linear velocity of the DVD (Step S7). Next, it is judged whetherthe value of M is "0" or an even value (Step S8). Since the value of Mis "0" at this state (Step S8 ; YES), the focus drive signal Sfd isoutputted in order to start to move up the bifocal lens 11 located atthe lower limit position at the first moving speed (Step S9, and referto a symbol (B) of FIG. 4). Then, it is judged whether or not any one ofthe peak values exceeds the threshold TH1 (refer to a symbol TH1 of FIG.1), for a focus error signal Sfe0 (refer to FIG. 4) detected at themoving up process (Step S11). Since the optical disk 1 is the CD in thisembodiment, the peak value of the focus error signal Sfe0 does notexceed the threshold TH1 as explained in FIG. 1 (Step S11; NO). Next, itis judged whether the value of M is "0" or the even value (Step S21).Since the value of M is "0" presently (Step S21; YES), it is judgedwhether or not the bifocal lens 11 is located at an upper limit position(Step S22). Namely, it is checked whether or not |Sfd|≧UH. In a casethat it is not located at the upper limit position (Step S22 ; NO), theoperation is returned to the step S8 in order to continue the moving upaction as it is. In a case of the upper limit position (Step S22; YES),M is increased (incremented) by "1" and set to "1" in this case (StepS23). It is judged whether or not the value of M is equal to or morethan "4" (Step S40). Since it is not "4" presently (Step S40; NO), theoperation is returned to the step S8.

Since the value of M is "1" at the step S8 (Step S8 ; NO), at this timethe focus drive signal Sfd is outputted in order to move down thebifocal lens 11 (Step S10, and refer to a symbol (C) of FIG. 4). It isjudged whether or not the peak value exceeds the threshold TH1 (refer tothe symbol TH1 of FIG. 1), for a focus error signal Sfe1 (refer toFIG.4) detected at the moving down process (Step S11). Since the opticaldisk 1 is presently assumed to be the CD, the peak value of the focuserror signal Sfe1 does not exceed the threshold TH1 similarly to theabove mentioned case (Step S11; NO). Next, it is judged whether thevalue of M is "0" or the even value (Step S21). Since the value of M is"1" presently (Step S21; NO), it is judged whether or not the bifocallens 11 is located at the lower limit position (Step S24). In a casethat it is not located at the lower limit position (Step S24; NO), theoperation is returned to the step S8 in order to continue the movingdown action as it is. In a case of the lower limit position (Step S24;YES), M is increased by "1" and set to "2" in this case (Step S23). Itis judged whether or not the value of M is equal to or more than "4"(Step S40). Since it is not "4" presently (Step S40; NO), the operationis returned to the step S8.

The above mentioned action is continued until the value of M becomes"3", and the bifocal lens 11 is reciprocated two times at the firstmoving speed. At this time, the focus error signals Sfe0 to Sfe3 (referto FIG. 4) do not exceed the threshold TH1, since the optical disk 1 isthe CD. Thus, the judgment result is always "NO" at the step S11.

When the value of M becomes "3" and the bifocal lens 11 is moved down(Step S10), then the value of M is increased by "1" at the step S23through the steps S11, S21 and S22, and set to "4" in this case. Thejudgment result becomes "YES" at the step S40. Thus, since the peakvalue of the focus error signals Sfe detected until that time does notexceed the threshold TH1 (refer to FIG.4), the optical disk 1 is judgedas the CD (Step S41). It is set such so as to carry out a later movingaction of the bifocal lens 11 at the second moving speed correspondingto the linear velocity of the record information recorded in the CD(slower than that of the DVD) (Step S42). It is judged whether or notthe value of M is equal to or more than "5" (Step S43). Since it is "4"presently (Step S43; NO), the operation is returned to the step S8.Since the value of M is "4" (Step S8; YES), the focus drive signal Sfdis outputted in order to move up the bifocal lens 11 located at thelower limit position at the second moving speed (Step S9, and refer to asymbol (D) of FIG.4). A focus error signal Sfe4 detected at this movingup process does not exceed the threshold TH1, since the optical disk 1is the CD (Step S11; NO). It is judged whether the value of M is "0" orthe even value (Step S21). Since it is "4" presently (Step S23; YES), itis judged whether or not the bifocal lens 11 is located at the upperlimit position (Step S22). In a case that it is not the upper limitposition (Step S22; NO), the operation is returned to the step S8 so asto continue the moving up action as it is. In a case of the upper limitposition (Step S22; YES), M is increased by 1 and set to "5" in thiscase (Step S23). It is judged whether or not the value of M is equal toor more than "4" (Step S40). Since the value of M is "5" presently (StepS40; YES), it is judged whether or not the value of M is equal to ormore than "5" through the steps S41 and S42 (Step S43). Since it is "5"presently (Step S43; YES), the value of M is decreased (decremented) by"1" and set to "4" in this case (Step S44). Then, the peak value of thefocus error signals Sfe4 is calculated in the servo controller 16 on thebasis of the focus error signal Sfe4 (Step S13). Then, the peak value atthe previous time is compared with the peak value at the current time(Step S14). In a case that the previous value is larger (Step S14; NO),the operation is shifted to the step S16. In a case that the currentvalue is larger (Step S14; YES), the current value is stored (Step S15),and the operation is shifted to the step S16. It is judged whether ornot the value of M is equal to or more than "4" (Step S16). Since it is"4" presently (Step S16; YES), the operation is waited for a waitingtime period T3 corresponding to the case of the CD so as to shift to aprocess after the peak value is calculated (Step S18). The value of M isincreased by "1" and set to "5" in this case (Step S19). It is judgedwhether or not the value of M is equal to or more than "8" (Step S20).Since it is "5" presently (Step S20; NO), the operation is returned tothe step S8. It is judged whether or not the value of M is "0" or theeven value (Step S8).

Since the value of M is "5" presently at the step S8 (Step S8; NO), theoperation is shifted to the step S10 in order to move down the bifocallens 11. Then, the bifocal lens 11 is moved down (Step S10). Similarly,the operations at the step S11 and the steps S21 to S24, and the stepsS40 to S44, and the steps S13 to S16, and the step S18 are carried out.The value of M is increased by "1" and set to "6" in this case (StepS19). The judgment result becomes "NO" at the step S20, and becomes"YES" at the step S8. Then, the operation is shifted to the step S9 inorder to move up the bifocal lens 11. The above mentioned actions arerepeated until the value of M becomes "8". The bifocal lens 11 isreciprocated two times at the second moving speed. Since all the peakvalues of the detected focus error signals Sfe4 to Sfe8 even in thiscase are equal to or less than the threshold TH1 (refer to FIG. 4), theoperation is always turned to the "NO" direction at the step S11.

When the value of M becomes "8" (Step S20; YES), the bifocal lens 11 isonce moved down to the lower limit position (Steps S26 and S27). A focusservo gain Gf is set (Step S28) by using the maximum value of the peakvalues stored (Step S15) until that time. After that, again the bifocallens 11 is moved up to the upper limit position (Steps S29 and S30). Thefocus servo loop is closed (Step S31) by using a focus error signal Sfe8detected at that time (refer to FIG. 4). Further for example, a trackingservo gain Gt is set (Step S32) by reading the peak value of thetracking error signal obtained on the basis of a three-beam method, aDPP (Differential Push-Pull) method and the like (Step S32), and thenthe reproduction of the record information is started (Step S33). Therising operation in a case that the optical disk 1 is the CD is ended asmentioned above. The timing chart of FIG. 4 shows the wave form of thefocus error signal Sfe and focus drive signal Sfd at this time.

On the other hand, in a case that the optical disk 1 is the DVD, any oneof focus error signals Sfe9 to Sfel2 detected while the value of M isranging from "0" to "3" exceeds the threshold TH1, as shown in FIG. 5(Step S11; YES). In this case, it is judged whether or not the value ofM is equal to or more than "4" at the step S12. Since it is equal to orless than "3" presently (Step S12; NO), then the actions at the stepsS13 to S20 are carried out. Incidentally, at the step 17, the operationis waited for a waiting period T2 corresponding to the case of the DVDfor shifting to a process after the peak value is calculated. While thevalue of M is ranging from "0" to "3", the bifocal lens 11 isreciprocated two times in upward and downward directions at the firstmoving speed, as shown in FIG. 5.

In a case that the value of M is "3", the value of M is set to "4" atthe step S19. The operation is returned to the step S9 through theprocessing of the steps S20 and S8, and then the focus drive signal Sfd(refer to a symbol (E) of FIG. 5) is outputted in order to move up thebifocal lens 11. The moving speed in this case is still the first movingspeed. When the bifocal lens 11 is moved up (Step S9), since the opticaldisk 1 is the DVD, the peak value of a detected focus error signal Sfe13exceeds the threshold TH1 (Step S1; YES, and refer to FIG.5). Further,since the value of M is "4" in this case (Step S12; YES), the opticaldisk 1 is judged as the DVD (Step S25). After that, the operationssimilar to the case in which the optical disk 1 is the CD (the steps S26to S33) are carried out. The rising operation in a case that the opticaldisk is the DVD is ended as mentioned above. The timing chart of FIG.5shows the wave form of the focus error signal Sfe and the focus drivesignal Sfd at this time. As can be seen from FIGS. 4 and 5, in a casethat the optical disk 1 is the DVD, the rising operation thereof isended in a shorter time than that of the CD.

As explained above, according to the present invention, at first, thetype of the optical disk 1 is judged on the basis of the focus errorsignal Sfe obtained at a time of moving the bifocal lens 11 at the firstmoving speed. When it is the DVD, the focus servo gain and the focusservo frequency band are set on the basis of the peak value as it is. Ina case that the optical disk 1 is judged as the CD, the bifocal lens 11is continuously moved at the second moving speed. The focus servo gainand the focus servo frequency band are set on the basis of the focuserror signals Sfe4 to Sfe8 obtained in conjunction with the abovementioned movement. As a result, it is possible to carry out the settingactions of the focus servo gain and the focus servo frequency band inthe effective manner and in the short time.

Also, it is possible to carry out the judgment of the optical disk 1 andthe setting actions of the focus servo gain and the focus servofrequency band in a series of actions.

As a result, it is possible to shorten a time needed for the risingoperation in the compatible reproducing apparatus which can reproduceboth the DVD and the CD.

In this embodiment, the threshold TH1 of judging the optical disk is setas a single value. However, if setting a threshold for the DVD and athreshold for the CD which is lower than that of the DVD, it is possibleto surely judge the CD and also possible to use the operational steps incommon to the DVD and the CD. By setting a plurality Df thresholds, itis easy for one skilled in the art to modify in such a way that thepresent invention is applied to judging of more than two kinds of theoptical disks.

Further, after the optical disk is judged, it is allowable to change themoving upper limit UH and the moving lower limit UL of the lens.Although the example in which the focus error signal is read every fourtimes is explained, it is not limited to this example. It is allowableto carry out at least one reading action or more. Furthermore, it isallowable to make the number of reading action different for each disktype as the occasion demands.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentinvention embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. An optical record medium judging method ofjudging types of optical record mediums, which distances from externalsurfaces thereof to information record surfaces thereof recorded withrecord information are different from each other, said method comprisingthe steps of:irradiating an information record surface of an opticalrecord medium to be reproduced with a light beam to be focused on one ofsaid information record surfaces of said optical record mediums on oneoptical axis; moving so as to change a relative distance parallel tosaid one optical axis between an objective lens for prescribing a focalpoint of the light beam and said information record surface, saidobjective lens; receiving a reflection light of the light beam reflectedfrom said information record surface, associated with a change of saidrelative distance; generating a focus error signal on the basis of thereceived reflection light; and judging a type of said optical recordmedium by comparing a level of the generated focus error signal with apredetermined standard level.
 2. A method according to claim 1, whereinthe types of said optical record mediums comprise a DVD and a CD.
 3. Amethod according to claim 1, wherein, in said focus error signalgenerating process, an S-shaped signal is generated as the focus errorsignal.
 4. A focus servo controlling method of judging types of opticalrecord mediums, on which record informations are recorded at linearvelocities different from each other, and setting a focus servo gain anda focus servo frequency band corresponding to one of the types of saidoptical record mediums, said method comprising the steps of:irradiatingan information record surface recorded with record information of anoptical record medium to be reproduced with a light beam to be focusedon an information record surface of said one of the types of saidoptical record mediums on one optical axis; moving, so as to change arelative distance parallel to said one optical axis between an objectivelens for prescribing a focal point of the light beam and saidinformation record surface, said objective lens; receiving a reflectionlight of the light beam reflected from said information record surface,associated with a change of said relative distance; generating a focuserror signal on the basis of the received reflection light; judging atype of said optical record medium by comparing a peak value of thegenerated focus error signal with a predetermined standard level; andsetting the focus servo gain and the focus servo frequency band on thebasis of the peak value.
 5. A method according to claim 4, wherein thetypes of said optical record mediums comprise a DVD and a CD.
 6. Amethod according to claim 4, wherein, in said focus error signalgenerating process, an S-shaped signal is generated as the focus errorsignal.
 7. An optical record medium judging apparatus for judging typesof optical record mediums, which distances from external surfacesthereof to information record surfaces thereof recorded with recordinformation are different from each other, said apparatus comprising:alight irradiating device for irradiating an information record surfaceof an optical record medium to be reproduced with a light beam to befocused on one of said information record surfaces of said opticalrecord mediums on one optical axis; a lens moving device for moving, soas to change a relative distance parallel to said one optical axisbetween an objective lens for prescribing a focal point of the lightbeam and said information record surface, said objective lens; a lightreceiving device for receiving a reflection light of the light beamreflected from said information record surface, associated with a changeof said relative distance; a focus error generating device forgenerating a focus error signal the basis of the received reflectionlight; and a judging device for judging a type of said optical recordmedium by comparing a level of the generated focus error signal with apredetermined standard level.
 8. An apparatus according to claim 7,wherein the types of said optical record mediums comprise a DVD and aCD.
 9. An apparatus according to claim 7, wherein said focus errorgenerating device generates an S-shaped signal as the focus errorsignal.
 10. A focus servo controlling apparatus for judging types ofoptical record mediums, on which record informations are recorded atlinear velocities different from each other, and setting a focus servogain and a focus servo frequency band corresponding to one of the typesof said optical record mediums, said apparatus comprising:a lightirradiating device for irradiating an information record surfacerecorded with record information of an optical record medium to bereproduced with a light beam to be focused on an information recordsurface of said one of the types of said optical record mediums on oneoptical axis; a lens moving device for moving, so as to change arelative distance parallel to said one optical axis between an objectivelens for prescribing a focal point of the light beam and saidinformation record surface, said objective lens; a light receivingdevice for receiving a reflection light of the light beam reflected fromsaid information record surface, associated with a change of saidrelative distance; a focus error generating device for generating afocus error signal on the basis of the received reflection light; a typejudging device for judging a type of said optical record medium bycomparing a peak value of the generated focus error signal with apredetermined standard level; and a servo setting device for setting thefocus servo gain and the focus servo frequency band on the basis of thepeak value.
 11. An apparatus according to claim 10, wherein the types ofsaid optical record mediums comprise a DVD and a CD.
 12. An apparatusaccording to claim 10, wherein said focus error generating devicegenerates an S-shaped signal as the focus error signal.
 13. A method forjudging a type of an optical record medium, comprising the stepsof:irradiating, through a lens, a surface of an optical record mediumwith a plurality of light beams, resulting in a plurality of reflectionsfrom the surface of the optical record medium; changing a distancebetween the lens and the surface of the optical record medium, resultingin another plurality of reflections from the surface of the opticalrecord medium; receiving the pluralities of reflections from the surfaceof the optical record medium; generating a plurality of error signalsfrom the pluralities of reflections; and comparing the error signalswith a predetermined standard to judge the type of optical recordmedium.
 14. A method for judging a type of an optical record medium asclaimed in claim 13, wherein the type of optical record medium comprisesa DVD and a CD.
 15. A method for judging a type of an optical recordmedium as claimed in claim 13, wherein the method judges whether theoptical record medium is the DVD or CD.
 16. A method for judging a typeof an optical record medium as claimed in claim 13, wherein the step ofcomparing the error signals comprises comparing a peak value of theerror signals with the predetermined standard to judge the type ofoptical record medium; and the method further comprises setting a focusservo gain and a focus servo frequency band based on the peak value. 17.An apparatus for judging a type of an optical record medium comprising:alight-irradiating device for irradiating, through a lens, a surface ofan optical record medium with a plurality of light beams; a lens-movingdevice for changing a distance between the lens and the surface of theoptical record medium; a light-receiving device for receiving aplurality of reflections from the surface of the optical record medium;an error-generating device for generating a plurality of error signalsfrom the plurality of reflections; and a judging device for comparingthe error signals with a predetermined standard to judge the type ofoptical record medium.
 18. An apparatus for judging a type of an opticalrecord medium as claimed in claim 17, wherein the type of optical recordmedium comprises a DVD and a CD.
 19. An apparatus for judging a type ofan optical record medium as claimed in claim 17, wherein the judgingdevice for comparing the error signals compares a peak value of theerror signals with the predetermined standard to judge the type ofoptical record median; and the apparatus further comprises aservo-setting device for setting a focus servo gain and a focus servofrequency band based on the peak value.
 20. An apparatus for judging atype of an optical record medium, comprising:means for irradiating,through a lens, a surface of an optical record medium with a pluralityof light beams, resulting in a plurality of reflections from the surfaceof the optical record medium; means for changing a distance between thelens and the surface of the optical record medium, resulting in anotherplurality of reflections from the surface of the optical record medium;means for receiving the pluralities of reflections from the surface ofthe optical record medium; means for generating a plurality of errorsignals from the pluralities of reflections; and means for comparing theerror signals with a predetermined standard to judge the type of opticalrecord medium.
 21. An apparatus for judging a type of an optical recordmedium as claimed in claim 20, wherein the type of optical record mediumcomprises a DVD and a CD, and wherein the apparatus judges whether theoptical record medium is the DVD or CD.
 22. An apparatus for judging atype of an optical record medium as claimed in claim 20, wherein themeans for comparing the error signals compares a peak value of the errorsignals with the predetermined standard to judge the type of opticalrecord medium; and the apparatus further comprises a means for setting afocus servo gain and a focus servo frequency band based on the peakvalue.